记一次CPU过高排查过程

存在的问题

上周突然在部署一点很简单的新业务之后，上线没多久突然OOM，大部分接口访问超时，甚至有的直接失败，刚开始以为是查询了什么了大数据导致的，结果看了下CPU，300%。

排查思路

最开始我先看了下日志，如下：

org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.PersistenceException: 
### Error querying database.  Cause: java.lang.IndexOutOfBoundsException: Index: 2, Size: 2
### The error may exist in file [/Users/bingfeng/Documents/mochuCode/service-ecook/target/classes/mybatis/mapper/CollectionSortMapper.xml]
### The error may involve cn.ecook.core.mapper.CollectionSortMapper.selectTopSortCollectionWithDays
### The error occurred while handling results
### SQL: select sortid as id ,count(*) as `number` from `collection_sort_collection`          WHERE  createtime between concat(?, ' 00:00:00') and concat(?, ' 23:59:59')          group by sortid         order by `number` DESC LIMIT ?
### Cause: java.lang.IndexOutOfBoundsException: Index: 2, Size: 2
	at org.mybatis.spring.MyBatisExceptionTranslator.translateExceptionIfPossible(MyBatisExceptionTranslator.java:92)
	at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:440)
	at com.sun.proxy.$Proxy97.selectList(Unknown Source)
	at org.mybatis.spring.SqlSessionTemplate.selectList(SqlSessionTemplate.java:223)
	at org.apache.ibatis.binding.MapperMethod.executeForMany(MapperMethod.java:147)
	at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:80)
	at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:93)
	at com.sun.proxy.$Proxy166.selectTopSortCollectionWithDays(Unknown Source)